The poll of 602 likely Republican caucusgoers was conducted over four days, from Dec. 27 to Dec. 30.

If the last two days of polling are considered by themselves, Santorum springs to second place, with 21 percent saying they would support him. Paul falls to 18 percent, with Romney remaining at 24 percent.

The full results have a margin of error of plus or minus 4 percentage points. The margin of error for the last two days is plus or minus 5.6 percentage points.

In June, the poll showed Michele Bachmann tied with Romney for first place; in August, Herman Cain joined the former Massachusetts governor at the top; Newt Gingrich led the pack in early December.